The present disclosure generally relates to pneumatic brake systems for heavy duty vehicles that make frequent stops in their vocation.
Pneumatic or air pressure-actuated brake systems for heavy duty vehicles are well known. Such brake systems utilize pressurized air to actuate a brake assembly in a brake chamber of the vehicle. Air actuation of the brake assembly is known in the art as a service brake application and is carried out to slow down or stop the vehicle while it is in motion. In addition to service brakes, it is common for heavy duty vehicles to include spring brakes, which are activated in a parking brake application to lock the brake assemblies in a park position when the vehicle is at rest. The brake assembly is locked in the park position through the expansion force of a spring located within the brake chamber, which is kept compressed in the non-activated state through application of air pressure. Actuation of the spring brakes is effected by venting or exhausting the pressurized air in the lines coupled to the brake chamber, and the spring brakes are deactivated by reintroducing pressurized air into the lines.
Normal operation of certain heavy duty vehicles that make frequent stops in their vocation (i.e., refuse, transit, school transportation and the like) demand frequent parking brake applications in a short period of time, which consume large volumes of compressed air. Such operations result in excessive brake system wear, undesirably reducing the useful life of the brake system components, and resulting in increased vehicle maintenance and repair costs.
It is also well known to provide a work brake system in addition to the conventional spring brakes for parking brake applications during start-and-stop operations of the heavy duty vehicle. Work brake systems generally utilize a service brake application, as if the operator were actuating the service brake pedals, with reduced air pressure from the normal service brake application to hold the vehicle in place. The work brake performs the function of a parking brake, but operates as a reduced pressure service brake.
Although the prior art park systems perform their respective functions, such park systems generally operate in an inefficient manner. Accordingly, there is a need for a park system that would provide a solution to one or more of the deficiencies from which the prior art park systems have suffered.